Dr. Christine Wu Nordahl has successfully completed the K99 phase of this award, and will continue on at UC Davis as an Assistant Professor for the ROO phase. Her laboratory will use structural and functional neuroimaging tola to gain understanding about the neuropathology of autism and the developing brain. The overarching research goal of this project is to use a multimodal structural and functional neuroimaging approach to investigating abnormalities in brain structure and connectivity in 2-4-year old children with autism. It is critical to evaluate brain abnormalities as close in time as possible to clinical diagnosis, during critical periods of brain development, and prior to intensive behavioral and medical interventions. Specifically, diffusion tensor imaging and resting state functional connectivity studies will be carried out to explore abnormalities in connectivity in very young children with autism. Additional goals include the evaluation of longitudinal brain growth trajectories during early development and the identification of subgroups or phenotypes within the autism diagnosis. Given the heterogeneity ofthe disorder, multiple etiologies and phenotypes likely exist. The identification of different brain phenotypes may aid in identifying more suitable treatments and interventions for particular subgroups of autism. The research will be carried out at the UC Davis M.I.N.D Institute and Imaging Research Center (IRC). All subject recruitment, diagnoses, and clinical training activities will be carried out at the M.I.N.D. Institute, a translational facility dedicated to developing a cure for autism. All neuroimaging will take place at the IRC, a research dedicated facility with pediatric imaging capabilities.